Rolling bearing unit with sensor

ABSTRACT

An outer ring  3  is provided with the stator  7  of a resolver  2,  and a ring member  4  with the rotor  8  of the resolver  2.  The stator  7  comprises an annular core  9  and a winding  10  provided around the core  9.  The ring member  4  is provided at a position opposed to the stator  7  with an eccentric cylindrical face serving as the rotor  8  and eccentric with respect to other outer peripheral surface of the ring member  4.

BACKGROUND ART

The present invention relates to antifriction bearing units having asensor for use in motor vehicle ABS or the like.

Antifriction bearing units are already known which comprise anantifriction bearing, and a sensor device and a pulser ring serving asthe portion to be detected, the sensor device and the pulser ring beingmounted on the bearing. Such units are used in railroad cars and motorvehicles for supporting an axle or a rotating shaft for transmittingrotation to the axle and for detecting rotation, i.e., the speed ofrotation of the axle or the angle of rotation.

It is strongly required that sensor-equipped antifriction bearing unitsof the type mentioned be improved in resolution in detecting rotationand reduced in diameter. In the case where the pulser ring is used, theresolution is dependent on the number of poles of the pulser ring whichare provided by magnetization, so that an improvement in resolutionrequires an increase in the number of poles. However, this results in alower magnetic flux density, diminishing the absolute value of signaloutput of the sensor device and entailing the problem that rotation canno longer be measured accurately. Thus, the improvement in resolution islimited.

Accordingly, JP-U No. 6-47867 discloses a sensor-equipped antifrictionbearing unit wherein the portion to be detected is used in place of thepulser ring. The disclosed unit has a generally U-shaped member to bedetected and having a plurality of projections, and a detecting portionpositioned between the projections so as to obtain an improved outputfor detecting the speed of rotation. Further JP-A No. 11-174069discloses a portion to be detected which is fitted around a nut forfixing a bearing device so as to provide a structure shaped withimproved accuracy and to improve the accuracy of detection.

The bearing unit disclosed in the first publication has the problem thatthe member to be detected is cumbersome to make. The bearing unit of thesecond publication has the problem that the unit is not usable forbearing devices having no nut.

It appears possible to obtain an antifriction bearing unit equipped witha sensor adapted to detect the state of rotation, utilizing a VR-typeresolver having high resolution and comprising a stator and a rotor.However, conventional VR-type resolvers have a special shape and made bysuperposing components which are prepared by drawing. When to be used asit is, therefore, the conventional resolver has the problem of makingthe bearing unit costly.

An object of the present invention is to provide an antifriction bearingunit having a sensor of high resolution and low cost, utilizing aresolver of reduced cost and high resolution.

DISCLOSURE OF THE INVENTION

The present invention provides a sensor-equipped antifriction bearingunit comprising an antifriction bearing having an outer ring member andan inner ring member, and a resolver for detecting the rotation of ashaft, one of the outer ring member and the inner ring member beingprovided with a stator of the resolver, the other ring member beingprovided at a position opposed to the stator with a face to be detectedand formed by machining for use as a rotor of the resolver.

The term “machining” as used herein does not mean joining of a member tobe made into a rotor to the outer ring member or inner ring member as bya press fit, but means to form the face of the rotor to be detected onan inner peripheral portion of the outer ring member which has a racewayon the inner periphery thereof, or on an outer peripheral portion of theinner ring member which has a raceway on the outer periphery thereof,for example, by cutting.

With the bearing unit of the present invention, one of the outer ringmember and the inner ring member is provided with a stator of theresolver, and other ring member is provided at a position opposed to thestator with a face to be detected and formed by machining for use as arotor of the resolver. Accordingly, there is no need to use anothermember anew for the rotor, and the resolver can be incorporated into theantifriction bearing compactly. The sensor-equipped antifriction bearingunit provided is therefore lower in cost and improved in resolution.

The principle of detecting the angle of rotation by the resolver isknown. When an outer ring member and an inner ring member rotaterelative to each other with sinusoidal voltage applied to the stator, anair gap between the stator and the face of the rotor to be detectedvaries continuously or discretely for the stator to produce a voltage inaccordance with the angle of rotation, whereby the state of rotation ofthe antifriction bearing unit can be detected. The stator and the rotorare made from a magnetic material. The outer ring or inner ring memberto be machined for forming a face for use as the rotor is made, forexample, from SUJ2. This ensures both the strength of the member as abearing raceway member and the magnetic characteristics of the rotor.

With the sensor-equipped antifriction bearing unit of the presentinvention, the outer ring is fixed, for example, to a housing, and arotating shaft or the like is fixed to a ring member, and the unit isused for supporting the rotating shaft and for detecting the state ofrotation of the shaft.

Various resolvers are usable which include brushless resolvers ofvarious types and brushless synchronous type, among which suitable areVR-type (variable-reactance type) resolvers.

The stator of the resolver comprises, for example, an annular corehaving a saw-toothed inner periphery, and a stator winding formed byproviding coils respectively on all teeth of the core. The stator isfixed to a shoulder portion of the outer ring member by a press fit,with the inner ends of the core teeth facing radially inward.

The rotor of the resolver is provided, for example, by machining theportion of the inner ring member opposed to the stator for use as arotor. The face thus formed and to be detected is in the form of aneccentric cylindrical face, namely, a cylindrical face which iseccentric with respect to the other outer peripheral surface(cylindrical surface concentric with the inner periphery of the outerring member) of the inner ring member. The eccentric cylindrical facecan be formed easily and accurately by machining the inner ring memberwith a cutting tool, with its axis positioned out of alignment with theaxis of the inner ring member.

The rotor face to be detected can be shaped variously insofar as it isin the form of a cylindrical face which is eccentric with respect to aperfect cylindrical face. The rotor face to be detected can be in theform of a cylindrical face centered about the axis of the antifrictionbearing and having a cutout. The cutout can be one in number, or aplurality of cutouts may be formed. These cutouts need not be arrangedequidistantly in the circumferential direction. The cylindrical facehaving such a cutout can be made easily and accurately, for example, bymaking an outer ring member or inner ring member in the same manner asconventionally, and thereafter forming an axially extending cutout inthe inner periphery or outer periphery of the member in the same manneras when forming a key groove. The cutout need not be limited to agroovelike form but may be, for example, in the form of a flat portionformed in the circumference.

In the case where the antifriction bearing is a single-row bearing, itis desirable to dispose the stator at one end of the bearing. When thebearing is a double-row bearing, it is of course acceptable to providethe stator at one end of the bearing, while when desired, the stator maybe disposed at an intermediate portion between the two rows of rollingbodies.

For example when rotation is to be detected for ABS using thesensor-equipped antifriction bearing unit, the rotation is detectablewith sufficient accuracy as required even if the rotor is in the form ofa simple eccentric cylindrical face or a cylindrical face having acutout. The use of the rotor of simple eccentric cylindrical face or acylindrical face having a cutout results in a reduced cost. Furthermore,there is no need to attach another rotor member to the rotatable ring,while the provision of the stator on the stationary ring realizes therotation detecting function described, consequently serving to provide acompacted bearing unit.

With the sensor-equipped antifriction bearing unit of the invention, theinner ring member is a rotation-side raceway member having a flange forattaching a wheel thereto and to be provided with the wheel, and theouter ring member is a stationary-side raceway member having a portionto be attached to a vehicle body side and-mountable on a vehicle body.The bearing unit thus constructed is incorporated as a hub unit intovehicles.

When to be used as a hub unit, the bearing unit has the followingconstruction.

The rotation-side raceway member comprises a shaft composed of alarge-diameter portion having a first raceway and a small-diameterportion having an outside diameter smaller than the diameter of thefirst raceway, and a ring having a second raceway and fitted around thesmall-diameter portion of the shaft.

In this case, it is desirable that the stator be disposed at an endportion of the stationary-side raceway member opposed to a shoulderportion of the ring of the rotation-side raceway member, and that theface of the rotor to be detected be formed on an outer periphery of theshoulder portion of the ring.

This construction makes it possible to take out a lead wire or connectorfor the stator from an end portion of the unit without the need to passsuch a member through a hole in the stationary-side raceway member byhand unlike the case wherein the stator is disposed between two rows ofrolling bodies of the hub unit. The unit can be assembled automaticallyin the same manner as in the prior art by performing only the additionalstep of forcing the stator into a hub unit by a press fit which unit hasno sensor device. This makes the sensor-equipped hub unit less costlyand compacted.

The wiring for the stator is led to the outside through an opening inthe end portion of the stationary-side raceway member in the form of ahollow cylinder, and a hollow cylindrical cover having a bottom isprovided over the end portion opening of the stationary-side racewaymember, the cover having at the bottom thereof a connector member to beprovided with a signal transmission harness. The stator is fixed to thecover, and the cover is fixed to the stationary-side raceway member.Alternatively, the stator may be fixed directly to the stationary-sideraceway member by a press fit without using an intervening cover. Awiring member including a lead wire and a connector pin is fixedlyembedded in a resin filling the interior thereof. In this way, thewiring for the stator can be led to the outside easily and free of thelikelihood of breaking.

The rotor face to be detected which is in the form of an eccentriccylindrical face can be provided easily with high accuracy, for example,by using a cutting tool with its axis out of alignment with the axis ofthe center axis of the inner peripheral surface of the ring whenmachining the outer periphery of the ring.

The sensor device is provided with a processing circuit for processingthe signal to be output in accordance with the air gap between thestator and the face of the rotor to be detected, i.e., the outerperipheral face of shoulder portion of the ring. Preferably, theprocessing circuit has a rotation sensor for determining the angle ofrotation or rotational speed required, for example, for ABS, and a wheelground contact load calculator for calculating the ground contact loadon the wheel from the air gap between the stator and the rotor.

With speed variations of the vehicle or alterations in the posturethereof, the ground contact load on each tire varies, and thedisplacement of the axis relative to the vehicle body varies with themagnitude of the ground contact load. The displacement of the axle is incorresponding relation with the displacement of the rotation-sideraceway member relative to the stationary-side raceway member in the hubunit, i.e., to the air gap between the stator and the rotor.Accordingly, by determining the relationship between the ground contactload on the tire and the displacement of the rotation-side racewaymember in advance, and measuring the air gap between the stator and therotor by the resolver, the ground contact load can be calculated fromthe ground contact load-displacement relational expression and from theair gap with high accuracy. The ground contact load on the tire thusobtained is used as substitute data for the slip ratio in ABS controland also for drive force control or brake force control, thuscontributing to improvements in vehicle control. Since the resolveritself detects rotation, rotation data is also available from theresolver along with the ground contact load, such that the importantparameters of wheel rotation and tire ground contact load can beobtained by a single sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in cross section showing a first embodiment ofsensor-equipped antifriction bearing unit according to the invention.

FIG. 2 is a view in section taken along the line II-II in FIG. 1.

FIG. 3 is a view in cross section showing a second embodiment ofsensor-equipped antifriction bearing unit according to the invention.

FIG. 4 is a view in section taken along the line IV-IV in FIG. 3.

FIG. 5 is a view in cross section showing a third embodiment ofsensor-equipped antifriction bearing unit according to the invention.

FIG. 6 is a view in section taken along the line VI-VI in FIG. 5.

FIG. 7 is a view in cross section showing a fourth embodiment ofsensor-equipped antifriction bearing unit according to the invention.

FIG. 8 is a view in section taken along the line VIII-VIII in FIG. 7.

FIG. 9 is an enlarged view of FIG. 8 showing the portion having aresolver attached thereto in detail.

FIG. 10 is a block diagram showing a processing circuit of thesensor-equipped antifriction bearing according to the fourth embodiment.

FIG. 11 is a sectional view showing a fourth embodiment ofsensor-equipped antifriction bearing unit according to the invention andcorresponding to FIG. 8 showing the fourth embodiment.

FIG. 12 is a block diagram showing a processing circuit of thesensor-equipped antifriction bearing according to the fifth embodiment.

FIG. 13 is a view corresponding to FIG. 9 showing another embodiment ofportion having a resolver attached thereto.

BEST MODE OF CARRYING OUT THE INVENTION

Embodiments of the invention will be described below with reference tothe drawings.

FIGS. 1 and 2 show a first embodiment of sensor-equipped antifrictionbearing unit of the invention. In the following description, the terms“left,” “right,” “upper” and “lower” refer respectively to the left- andright-hand sides and upper and lower sides of FIG. 1.

As shown in FIGS. 1 and 2, the bearing unit comprises an antifrictionbearing 1 serving as a bearing, and a resolver 2 for detecting therotation thereof.

The antifriction bearing 1 comprises an outer ring 3 serving as astationary ring, a ring member 4 serving as a rotatable ring, balls 5serving as rolling bodies arranged between the ring 3 and the ringmember 4, and a retainer 6. Although not shown, the outer ring 3 isfixed to a housing or the like, and the ring member 4 has a rotatingshaft or the like fixed thereto.

The resolver 2 is a VR-type brushless resolver, and comprises a stator 7and a rotator 8. The stator 7 is provided on the outer ring 3, and therotor 8 on the ring member 4.

The stator 7 comprises an annular core 9 having a saw-toothed innerperiphery, and a stator winding 10 formed by providing coilsrespectively on all teeth 9 a of the core 9. The stator 7 is fixed tothe right end of the outer ring 3 by a press fit, with the inner ends ofthe core teeth 9 a facing radially inward, whereby the inner peripheryof the core 9 of the stator 7 is made concentric with the innerperiphery of the outer ring 3. The core 9 has an inside diameterslightly larger than the outside diameter of the ring member 4.

The rotor 8 of the resolver 2 is provided by machining the portion ofthe ring member 4 facing the stator 7, i.e., a right end portion of thering member 4, for use as a rotor. The rotor 8 is in the form of acylindrical face having a center axis positioned slightly below the axisof the ring member 4. Thus, the rotor 8 is in the form of a cylindricalface which is eccentric with respect to the other outer peripheralsurface 4 a of the ring member 4. Accordingly, when the ring member 4rotates, the gap between the stator core 9 having an inner peripheryconcentric with the inner periphery of the outer ring 3 and the rotor 8comprising the eccentric cylindrical face alters, producing a voltage inaccordance with the angle of rotation on the stator 7. The voltage issent to a processing circuit through a signal line 11, whereby the stateof rotation of the rotating shaft can be detected as required, forexample, for ABS.

FIGS. 3 and 4 show a second embodiment of sensor-equipped antifrictionbearing unit of the invention. In the following description, the terms“left,” “right,” “upper” and “lower” refer respectively to the left- andright-hand sides and upper and lower sides of FIG. 3.

As shown in FIGS. 3 and 4, the sensor-equipped bearing unit comprises anantifriction bearing 21 serving as a bearing, and a resolver 22 fordetecting the rotation thereof.

The antifriction bearing 21 is a double-row angular ball bearing andcomprises an outer ring member 23 serving as a stationary ring, twoinner ring members 24 serving as rotatable rings, balls 25 serving asrolling bodies arranged in two rows between these members 23, 24, andretainers 26 for holding the balls 25 in the respective rows. Althoughnot shown, the outer ring member 23 is fixed to a housing or the like,and the inner ringmembers 24 have a rotating shaft or the like fixedthereto.

The resolver 22 is a VR-type brushless resolver, and comprises a stator27 and a rotator 28. The stator 27 is provided on the outer ring member23, and the rotor 28 on the inner ring member 24.

The stator 27 comprises an annular core 29 having a saw-toothed innerperiphery, and a stator winding 30 formed by providing coilsrespectively on all teeth 29 a of the core 29. The stator 27 is fixedapproximately to the axial midportion of the outer ring member 23 by apress fit, with the inner ends of the core teeth 29 a facing radiallyinward, whereby the inner periphery of the core 29 of the stator 27 ismade concentric with the inner periphery of the outer ring member 23.The core 29 has an inside diameter slightly larger than the outsidediameter of the inner ring members 24.

The rotor 28 of the resolver 22 is provided by machining the portion ofthe inner ring member 24 facing the stator 27 for use as a rotor. Thestator 27 is positioned as slightly shifted rightward from the axialmidpoint of the outer ring member 23 so that the core 29 thereof isopposed to the left end portion of the inner ring member 24 at theright. The right end portion only of the right inner ring member 24 ismachined for use the rotor. The rotor 28 is in the form of a cylindricalface having a center axis positioned slightly below the axis of theinner ring member 24. Thus, the rotor 28 is in the form of an eccentriccylindrical face having an axis out of alignment with the axis of theother outer peripheral surface 24 a of the inner ring member 24.Accordingly, when the inner ring members 24 rotate, the gap between thestator core 29 having an inner periphery concentric with the innerperiphery of the outer ring member 23 and the rotor 28 comprising theeccentric cylindrical face alters, producing a voltage in accordancewith the angle of rotation on the stator 27. The voltage is sent to aprocessing circuit through a signal line 31, whereby the state ofrotation of the rotating shaft can be detected as required, for example,for ABS.

With the first and second embodiments described above, the outer ring 3or 23 is the stationary side, and the ring member 4 or 24 is therotatable side, whereas the outer ring 3 or 23 may serve as therotatable side, and the ring member 4 or 24 as the stationary side. Inthis case, it is preferable to provide the rotor on the inner peripheryof the outer ring 3 or 23, and the stator on the outer periphery of thering member 4 or 24.

FIGS. 5 and 6 show a third embodiment of sensor-equipped antifrictionbearing unit of the invention. In the following description, the terms“left,” “right,” “upper” and “lower” refer respectively to the left- andright-hand sides and upper and lower sides of FIG. 5.

As shown in FIGS. 5 and 6, the sensor-equipped antifriction bearing unitcomprises a hub unit 41 serving as a bearing, and a resolver 42 fordetecting the rotation thereof.

The hub unit 41 comprises an outer ring member 43 serving as astationary-side raceway member fixed to a vehicle body (hereinafterreferred to as the “body-side raceway member”), an inner ring member 44serving as a rotation-side raceway member to which a wheel is to beattached (hereinafter referred to as the “rotation-side racewaymember”), balls 45 serving as rolling bodies arranged in two rowsbetween the two members 43, 44, and retainers 46 for holding the balls45 in the respective rows.

The body-side raceway member 43 has a hollow cylindrical portion 52provided with two outer ring raceways on the inner periphery thereof,and a flange portion 53 provided in the vicinity of the left end of thecylindrical portion 52 and to be fastened with bolts to a suspensiondevice (vehicle body). The rotation-side raceway member 44 comprises ashaft 54 composed of a large-diameter portion 55 having a first raceway55 a, and a small-diameter portion 56 having an outside diameter smallerthan the diameter of the first raceway 55 a; and a ring 57 fixedlyfitted around the small-diameter portion 56 of the shaft 54. The shaft54 has an externally threaded left end portion. A nut 58 is screwed onthe externally threaded portion for holding the ring 57 in intimatecontact with the left end face of the large-diameter portion 55 of theshaft 54. The shaft 54 has a flange 60 positioned close to the right endthereof and fixedly provided with bolts 59 for attaching the wheel. Thering 57 has a raceway 57a in parallel to the raceway 55 a of the shaft55. A seal device 61 is provided between the right end of the body-sideraceway member 43 and the shaft 55.

The resolver 42 is a VR-type brushless resolver, and comprises a stator47 and a rotator 48. The stator 47 is provided on the body-side racewaymember 43, and the rotor 48 on the rotation-side raceway member 44.

The stator 47 comprises an annular core 49 having a saw-toothed innerperiphery, and a stator winding 50 formed by providing coilsrespectively on all teeth 49 a of the core 49. The stator 47 is fixedapproximately to the axial midportion of the body-side raceway member 43by a press fit, with the inner ends of the core teeth 49 a facingradially inward, whereby the inner periphery of the core 49 of thestator 47 is made concentric with the inner periphery of the body-sideraceway member 43. The core 49 has an inside diameter slightly largerthan the outside diameter of the large-diameter portion 55 of the shaft54.

The rotor 48 of the resolver 42 is provided by machining the portion ofthe rotation-side raceway member 44 facing the stator 47 for use as arotor. The stator 47 is positioned as opposed to a portion of the shaft54 close to the left end of the large-diameter portion 55 thereof. Theleft end part of large-diameter portion 55 of the shaft 54 is machinedfor use the rotor. The rotor 48 is in the form of a cylindrical facehaving a center axis positioned slightly below the axis of therotation-side raceway member 44. Thus, the rotor is in the form of acylindrical face which is eccentric with respect to the other outerperipheral surface of large-diameter portion of the shaft 54.Accordingly, when the rotation-side raceway member 44 rotates, the gapbetween the stator core 49 having an inner periphery concentric with theinner periphery of the body-side raceway member 43 and the rotor 48comprising the eccentric cylindrical face alters, producing a voltage inaccordance with the angle of rotation on the stator 47. The voltage issent to a processing circuit through a signal line 31, whereby the stateof rotation of the rotating shaft can be detected as required, forexample, for ABS.

With the sensor-equipped antifriction bearing unit according to thethird embodiment, the rotation-side raceway member 44 comprises a shaft54 and a ring 57 integral therewith, so that when the unit is used as abearing for the motor vehicle wheel, the bearing portion can becompacted and made lightweight.

FIGS. 7 and 8 show a fourth embodiment of sensor-equipped antifrictionbearing unit of the invention.

As shown in FIGS. 7 and 8, the sensor-equipped antifriction bearing unitcomprises a hub unit 71 serving as a bearing, and a resolver 72 servingas a sensor device for detecting the rotation thereof and ground contactload.

The hub unit 71 comprises a stationary-side raceway member 73 fixed to avehicle body, a rotation-side raceway member 74 to which a wheel is tobe attached, balls 75 serving as rolling bodies arranged in two rowsbetween the two members 73, 74, and retainers 76 for holding the balls75 in the respective rows.

The stationary-side raceway member 73 has a hollow cylindrical portion82 provided with two outer ring raceways on the inner periphery thereof,and a flange portion 83 provided in the vicinity of the left end of thecylindrical portion 82 and to be fastened with bolts to a suspensiondevice (vehicle body).

The rotation-side raceway member 74 comprises a shaft 84 composed of alarge-diameter portion 85 having a first raceway 85 a, and asmall-diameter portion 86 having an outside diameter smaller than thediameter of the first raceway 85 a; and a ring 87 fixedly fitted aroundthe small-diameter portion 86 of the shaft 84 and having a right face inintimate contact with the left face of large-diameter portion 85 of theshaft 84. The shaft 84 has a flange 88 positioned close to the right endthereof and fixedly provided with bolts 89 for attaching the wheel. Thering 87 has at its right portion a raceway 87 a in parallel to theraceway 85 a of the shaft 84. The ring 87 has a shoulder portion 87 b atits left portion. A seal device 90 is provided between the right end ofthe stationary-side raceway member 73 and the shaft 84. A cover 91 isfixedly provided over the left end portion of the stationary-sideraceway member 73. The cover 91 is in the form of a bottomed hollowcylinder made of metal or resin and provided at the right end thereofwith a hollow cylindrical fixed portion 91 a fixedly fitting to theinner periphery of the left end portion of the stationary raceway member73.

The resolver 72 is a VR-type brushless resolver and comprises a stator77 and a rotor 78. The stator 77 is provided on the fixed portion 91 aof the cover 91 and positioned as opposed to the ring shoulder portion87 b. The rotor 78 is positioned as opposed to the stator 77, i.e., onthe shoulder portion 87 b of ring 87 of the rotation-side raceway member74. The stator 77 delivers a signal to the outside via a wiring memberincluding a lead wire 93 and a connector pin 94.

As shown in detail in FIG. 8, the stator 77 comprises an annular core 79having a saw-toothed inner periphery, and a stator winding 80 formed byproviding coils respectively on all teeth 79 a of the core 79. Thestator 77 is fixed to the inner periphery of fixed portion 91 a of thecover 91 by a press fit, with the inner ends of the core teeth 79 afacing radially inward.

As shown on an enlarged scale, the fixed portion 91 a of the cover 91fixedly fitted to the inner periphery 73 a of the left end portion ofthe stationary-side raceway member 73 is provided on the left sidethereof with an annular ridge 91 b projecting radially outward and inbearing contact with an axially outer end face of the left end portionof the member 73. The bottom of the cover 91 is provided with aconnector member 91 c to which signal transmitting-receiving harness isto be attached. The output of the stator winding 80 is delivered to theconnector pin 94 through the lead wire 93. The lead wire 93, connectorpin 94 and stator 77 are fixedly embedded in a resin 92 filling theinterior of the cover 91. The core 79 of the stator 77 is left exposedfrom the resin only at the portion thereof opposed to the rotor 78. Theconnector member 91 c at the bottom of the cover 91 is also made ofresin, and the connector pin 94 is provided inside the connector member91 and has an outer end projecting from the resin 92. A plurality oflead wires 93, as well as of connector pins 94, are provided for usewith different signals. Thus, the stator 77 and wiring members 93, 94therefor are provided only on the cover 91, so that the stator 71 andwiring therefore can be arranged and connected without the likelihood ofwires breaking.

As shown in FIG. 9, the stationary-side raceway member 73 has close toits left end portion a stopper portion 73 b having a diameter slightlysmaller than the diameter of the left-end opening of the member 73. Theright end of fixed portion 91 a of the cover 91 comes into contact withthis stopper portion 73 b when the cover is placed in from the leftrightward, whereby the stator 77 is precisely positioned in place asopposed to the ring 87. The stator 77 is forced into the left endportion of the stationary-side raceway member 73 by the cover 77 in thisway, whereby the inner periphery of the stator core 79 is madeconcentric with the inner periphery of the raceway member 73. The insidediameter of the core 79 is slightly larger than the outside diameter ofthe shoulder portion 87b of the ring 87.

The face of the rotor 78 of the resolver 72 to be detected is providedby machining the portion of the ring 87 opposed to the stator, i.e., theouter periphery of the shoulder portion 87 b, for use as a rotor. Asseen in FIGS. 7 and 8, the face of the rotor 78 to be detected is in theform of a cylindrical face having a center axis which is positionedslightly above the axis of the hub unit 71, i.e., the center axis of thestator 77. Thus, the rotor face to be detected is in the form of acylindrical face which is eccentric with respect to the inner peripheralsurface of the stator 77. Accordingly, when the rotation-side racewaymember 74 rotates, the gap between the stator core 79 and the face(eccentric cylindrical face) to be detected of the rotor 78 alters,producing a voltage in accordance with the angle of rotation on thestator 77. Thus variations in the voltage of the stator 77 are sent to aprocessing circuit through a signal line (not shown), whereby the stateof rotation of the rotating shaft can be detected as required, forexample, for ABS.

With the sensor-equipped antifriction bearing units of the third andfourth embodiments, variations in the ground contact load on the tirevaries the displacement of the rotation-side raceway member 44 or 74relative to the stationary-side raceway member 43, 73, consequentlyvarying the air gap between the stator 47 or 77 and the rotor 48 or 78to be detected by the resolver 42 or 72. As shown in FIG. 10, variationsin the air gap are output from the resolver 42, 72 as variations involtage. Data, such as angle of rotation or rotational speed, required,for example, for ABS is determined based on the output signal by therotation sensor of the processing circuit for the resolver (sensordevice). The processing circuit for the resolver further has a groundcontact load calculator having calculation equations stored therein forcalculating the ground contact load from the displacement output as avoltage variation. The calculator calculates the ground contact load,which is fed to vehicle control means to control the vehicle properly.

FIG. 11 shows a fifth embodiment of sensor-equipped antifriction bearingunit according to the invention. This embodiment differs from the fourthembodiment only with respect to the shape of the rotor 78. Thedifference only will be described below, and throughout the drawingsconcerned, like parts are referred to by like reference numerals andwill not be described repeatedly. The rotor 78 of this embodiment hasexactly the same shape as the one shown in FIG. 7 invertical section. Aswill be apparent from FIG. 11 corresponding to FIG. 8, a cutout 81 isformed in a cylindrical face concentric with the axis of the hub unit71, i.e., the center axis of the stator 77, in place of an eccentriccylindrical face to provide the face of the rotor 78 to be detected.

With the sensor-equipped antifriction bearing unit according to thefifth embodiment, the displacement of the rotation-side raceway member74 varies relative to the stationary-side member 73 when the groundcontact load on the tire varies, consequently varying the air gapbetween the stator 77 and the rotor 78 to be detected by the resolver72. As shown in FIG. 12, variations in the air gap are output from theresolver 72 as voltage variations. The air gap in the fourth embodimentgently varies with a relatively great amplitude since the face of therotor 78 to be detected is in the form of an eccentric cylindrical face,whereas variations in the air gap in the fifth embodiment are in theform of a waveform of relatively small amplitude and pulselike peakvalues as superposed on the waveform since the face of the rotor 78 tobe detected is in the form of a cylindrical face having a cutout 81.Based on the pulselike peak values of the output signal, the angle orrotation or rotational angle is determined as required, for example, forABS by the rotation sensor of the processing circuit of the resolver(sensor device). The resolver processing circuit further has a groundcontact load calculator having stored therein calculating equations forcalculating the ground contact load from the waveform included in thevariations and other than the pulselike peak values. The ground contactload is obtained by the calculator, and the load obtained is fed tovehicle control means for properly controlling the vehicle.

According to the embodiments shown in FIGS. 7 and 9, the stator 77 isinstalled in place by fixing the stator 77 to the cover 91 by a pressfit, and fixing the cover 91 to the stationary-side raceway member 73 tofix the stator 77 thereto. However, the stator 77 may be fixed directlyto the inner periphery 73 a of the left end portion of thestationary-side raceway member 73 by a press fit as shown in FIG. 13.The stator 77 can be installed in this way by forcing the stator 77 intocontact with the stopper portion 73 b of the member 73, and thereafterfixedly fitting the cover 91 to the inner periphery 73 a of the left endportion of the raceway member 73.

With this embodiment, a connector 95 is attached to the outer end of thelead wire 93 from the stator winding 80. A connector member 91C at thebottom of the cover 91 is made from resin like the one shown in FIG. 6,and a connector pin 94 is disposed inside the connector member 91 c withits outer end projecting from the resin 92. Connected to the connectorpin (end connector) 94 by a lead wire 97 is an intermediate connectorpin 96. These pins 94, 96 and the lead wire 97 are fixedly embedded inthe resin 92 filling the interior of the cover 91, with the outer endsof the pins 94, 96 left exposed. The lead wire 93 and the connector 95closer to the stator winding 80 are separated from the resin 92. Thewiring of this embodiment is connectable by fixing the stator 77 to thestationary-side raceway member 73 by a press fit and thereafter joiningthe connector 95 closer to the stator 77 to the intermediate connectorpin 96 closer to the cover 91. The cover 91 having the connector pins94, 96 and the lead wire 97 embedded inside thereof is then fixed to theraceway member 73 by a press fit. In this way, the wiring for the stator77 can be completed easily without the likelihood of breaking.

INDUSTRIAL APPLICABILITY

When various antifriction bearings as of hub units of motor vehicles arereplaced by the sensor-equipped antifriction bearing unit of theinvention, sensor devices for detecting various data as to the motorvehicle can be provided in the form of antifriction bearing units,whereby useful data is available for controlling the vehicle to achieveimprovements in the control of the motor vehicle.

1. A sensor-equipped antifriction bearing unit comprising anantifriction bearing having an outer ring member and an inner ringmember, and a resolver for detecting the rotation of a shaft, one of theouter ring member and the inner ring member being provided with a statorof the resolver, the other ring member being provided at a positionopposed to the stator with a face to be detected and formed by machiningfor use as a rotor of the resolver.
 2. A sensor-equipped antifrictionbearing unit according to claim 1 wherein the face of the rotor to bedetected is in the form of a cylindrical face eccentric with respect toa cylindrical surface centered about an axis of the antifrictionbearing.
 3. A sensor-equipped antifriction bearing unit according toclaim 1 wherein the face of the rotor to be detected is in the form of acylindrical face centered about an axis of the antifriction bearing andhaving a cutout.
 4. A sensor-equipped antifriction bearing unitaccording to claim 1 wherein the antifriction bearing is a double-rowbearing, and the stator is disposed at an intermediate portion betweentwo rows of rolling bodies.
 5. A sensor-equipped antifriction bearingunit according to claim 1 wherein the resolver is a VR-type resolver. 6.A sensor-equipped antifriction bearing unit according to claim 1 whereinthe inner ring member is a rotation-side raceway member having a flangefor attaching a wheel thereto and to be provided with the wheel, and theouter ring member is a stationary-side raceway member having a portionto be attached to a vehicle body side and mountable on a vehicle body.7. A sensor-equipped antifriction bearing unit according to claim 6wherein the rotation-side raceway member comprises a shaft composed of alarge-diameter portion having a first raceway and a small-diameterportion having an outside diameter smaller than the diameter of thefirst raceway, and a ring having a second raceway and fitted around thesmall-diameter portion of the shaft.
 8. A sensor-equipped antifrictionbearing unit according to claim 7 wherein the stator is disposed at anend portion of the stationary-side raceway member opposed to a shoulderportion of the ring of the rotation-side raceway member, and the face ofthe rotor to be detected is formed on an outer periphery of the shoulderportion of the ring.
 9. A sensor-equipped antifriction bearing unitaccording to claim 8 wherein wiring for the stator extends to theoutside through an opening in the end portion of the stationary-sideraceway member in the form of a hollow cylinder, and a hollowcylindrical cover having a bottom is provided over the end portionopening of the stationary-side raceway member, the cover having at thebottom thereof a connector member to be provided with a signaltransmission harness.
 10. A sensor-equipped antifriction bearing unitaccording to claim 9 wherein the stator is fixed to the cover, and thecover is fixed to the stationary-side raceway member.
 11. Asensor-equipped antifriction bearing unit according to claim 9 wherein awiring member including a lead wire and a connector pin is fixedlyembedded in a resin filling interior thereof.